1. Field of the Invention
This invention relates broadly to explosively driven fasteners More particularly, this invention relates to an apparatus for installing explosively driven fasteners and fasteners for use therewith.
2. State of the Art
Various forms of explosively actuated fastener systems have been developed to drive fasteners into hard structures such as wood, concrete, masonry and steel. A considerable advantage of using such fastener systems has been the reduced time required for installing the fasteners into hard structures. However, a major common disadvantage is that the fasteners cause high stresses when penetrating into the receiving material in the region of the fastening whereby greater spalling occurs. In addition, explosively actuated fastener systems are relatively complex in construction and costly to manufacture and, due to inadequate venting of their combustion chamber, suffer from the disadvantages that they are relatively noisy and tend to jam from a buildup of spent powder.
Explosively actuated fastener systems have been previously divided into two general groups: the low-velocity fastener system (discharging fasteners at a velocity of less than about 300 ft/sec) and the high-velocity fastener system (discharging fasteners at a velocity of greater than about 500 ft/sec). In the low velocity systems, a drive pin is positioned at the exit end of a cylindrical barrel with a piston located inwardly and spaced from the drive pin and an explosive charge located behind the piston. In the high velocity systems, a drive pin is positioned behind the piston. Some high-velocity fastener systems still have the disadvantages of high noise level, dangerous free fastener velocity and high degree of spall and ricochet when the drive pin strikes the work surface. Some low-velocity fastener systems still have the disadvantage of high noise level, power limitation, severe spall out in concrete and high incidence of drive pin damage.
With the fastener systems being ballistic in nature and the fasteners attaining free flight, the fastener systems have incurred safety concerns analogous to those of firearms. Designs of power loads have been adjusted to make systems safer, to reduce the number of required parts, and thus decrease the cost of production.
U.S. Pat. No. 3,172,123 discloses an explosive actuated tool in which a spring-loaded barrel with a bore is forced toward a work surface, thus forcing a fastener into the bore of the barrel. The fastener acts as a firing pin for igniting a power charge disposed at a head end of the fastener.
U.S. Pat. No. 3,514,025 discloses an electrically operated explosively actuated tool using a caseless cartridge.
U.S. Pat. No. 3,665,583 describes a suspension clip structure which includes a center portion and a projecting retaining flange for facilitating the holding of the suspension clip structure on a power actuated tool.
U.S. Pat. No. 3,797,721 describes an explosive actuated tool for driving a fastening stud. The tool includes a barrel with a bore. A muzzle is provided at one end of barrel and an explosion chamber communicates with the bore. A closed gas expansion chamber surrounds the barrel and communicates with the bore solely through a plurality of passageways in the barrel adjacent to the muzzle.
U.S. Pat. No. 4,830,254 describes a two-stage power driving system for powder actuated tools comprising a barrel, a piston, a first stage power load activation means and a power amplifier. The power amplifier accommodates a stacked arrangement of a fastener and a second stage power load.
U.S. Pat. No. 4,890,778 describes a hammer-activated fastener tool for driving fastener projectiles comprising a relatively movable barrel and housing components. The barrel carries a power load chamber body and a relatively movable piston member which in muzzleward movement drives the fastener object and on breechward movement achieves ejection of the spent power load cartridge. The housing carries a movable firing pin assembly.
U.S. Pat. No. 4,899,919 briefly describes a self-energizing fastener which comprises a nail and a charge pellet attached to the head of the nail. A generally cylindrical tool with an “igniting projection” is also shown.
U.S. Pat. No. 5,016,802 describes an explosive actuated extendable driving tool having a housing with a barrel at its front end for receiving a fastening element, with a load chamber in an inner end of the barrel. A manually actuated reciprocating shaft is slidably received in a retainer that is mounted to the back end of the housing. A muzzle with a self-aligning spall guard and splash guard are mounted to the barrel, with a noise suppression element being contained in a chamber formed between the spall guard and the splash guard. Exits for the discharge of combustion gases and carbon into the noise suppression element are defined by discharge ports formed in the barrel and spall guard.
U.S. Pat. No. 5,135,150 describes a pole-type powder actuated tool that includes a first pin having a flange at the top end, a second pin having a flange at the top end in contact with the flange of the first pin so that the second pin will move in unison with the first pin, a front barrel for receiving a drive pin and cartridge, a rear barrel for accommodating the second pin and part of the first pin and engaged with the front barrel at one end and with a connecting pipe at the other end, two springs enclosing the first pin and second pin for forcing the two pins to the normal position after fired.
U.S. Pat. Nos. 5,544,800, 5,497,929, and 5,423,469 describe a system for driving a fastener into a work surface. The system includes a fastener having a penetration end, a shaft and a receptacle head end for receiving a power charge and a tool having a reciprocating firing pin. The tool includes a barrel with a bore having a muzzle for receiving the fastener, a spring-biased firing pin and an exhaust chamber connected to the bore for receiving exhaust gases.
U.S. Pat. No. 5,904,284 describes an explosively actuated fastener system. The explosively actuated fastener system includes a front end; a back end; an open-ended muzzle being positioned adjacent to the front end of the fastener system; an open-ended outer tubular member having a front end and a back end; an open-ended tubular cap being attached to the back end of the outer tubular member and having a front end and a back end and an inward circular protrusion at the back end; an open-ended barrel member including an axial, central bore and extending from within, being an integral continuation of, and thus connecting, the muzzle to the outer tubular member; an open-ended inner tubular member having a front end and a back end, with an outward circular protrusion and an inward circular protrusion being positioned at the front end; a reciprocating ejector comprising a retaining section positioned in the inner tubular member, an outward circular protrusion and a firing rod, that extends forwardly from the retaining section, that comprises a front section, a middle section and a back section and that is separated from the retaining section by the outward circular protrusion; an ejector housing being used for accommodating the reciprocating ejector and including a tube, an outward circular protrusion and a firing pin that extends forwardly from the tube, with the tube including a closed top, an open bottom, a front section that is smaller in diameter than the axial, central bore of the barrel member, a middle section and a back section that is separated from the middle section by the outward circular protrusion and that has a number of perforations; a forward spring being positioned within the inner tubular member; a balancing spring being positioned within the outer tubular member; a handle being attached to and serving as a closure for the back end of the inner tubular member; an open-ended sliding guide including a tubular main body and a front part that at its front edge has an inward circular protrusion and being positioned in front of the outward circular protrusion of the inner tubular member and within the outer tubular member; a reset spring being fitted around the front part of the sliding guide and being positioned between the outward circular protrusion of the ejector housing and the main body of the sliding guide and a pin means being fitted in the number of perforations in the back section of the ejector housing.
According to the method of the '284 patent, the handle is first pulled backwards to manually reset the fastener system. The backward movement of the inner tubular member results in opening up of the reset spring, causes the sliding guide to move backward and, thus, causes the pin means to lock. Upon pulling the handle to bring the fastener system to a set position, the handle is pushed forward. The forward push on the handle results in compression of the forward spring and build-up of a striking force that forces the inner tubular member to move forward. The forward movement of the inner tubular member causes the sliding guide to move forward and results in compression of the reset spring. The pin means is unlocked, allowing the forward spring to open up, and the firing rod moves forward, pushed by the opening forward spring, in the ejector housing and strikes front of the tube and the firing pin of the ejector housing which initiates deflagration or detonation of a solid propellant pill.